Magnetic Memory Stack With Rare-Earth Oxide for Low-Current Writing
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Solution Overview
Problem
Existing magnetic memory devices face challenges in reducing the product of saturation magnetization (Mst) of the storage layer while minimizing increases in write current (Ic) and decreases in thermal stability (Δ), which are exacerbated by agglomeration and surface roughness issues in thin storage layers.
Innovation Solution
Incorporating an oxide layer adjacent to the storage layer containing a rare earth element and boron (B) improves perpendicular magnetic anisotropy, enhancing wettability and reducing agglomeration, thereby allowing for a thinner storage layer without increasing write current or decreasing thermal stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the storage layer is made thinner to reduce Mst, then the write error rate improves, but agglomeration and surface roughness occur which increase write current and decrease thermal stability
Solution Approach 1:
An oxide layer containing rare earth elements (Gd, Sc, or Y) is introduced as an intermediary layer between the storage layer and the tunnel barrier layer. This oxide layer acts as a mediator that suppresses agglomeration and improves wettability at the storage layer interface, enabling thinner storage layers to be formed without surface roughness issues, thereby reducing write error rate while maintaining manufacturing precision
Solution Approach 2:
The composition of the oxide layer is specifically controlled with rare earth element content at 5-50 at% and a thickness of 0.5-5 nm. By adjusting these parameters, the oxide layer optimally suppresses agglomeration and controls perpendicular magnetic anisotropy, allowing the storage layer to be made thinner while preventing surface roughness and maintaining thermal stability
2Use of energy by moving object
If the storage layer is made thinner to reduce Mst, then the write current decreases, but thermal stability decreases
Solution Approach 1:
The oxide layer containing rare earth elements serves as an intermediary that enhances perpendicular magnetic anisotropy at the storage layer interface. This increased perpendicular magnetic anisotropy compensates for the reduced thermal stability that would normally result from thinning the storage layer, allowing thinner layers to maintain adequate thermal stability while reducing write current
Solution Approach 2:
The introduction of an oxide layer composite structure between the storage layer and tunnel barrier layer creates a composite magnetic tunnel junction. The rare earth element oxide composite provides enhanced perpendicular magnetic anisotropy that compensates for the reduced thermal stability of thinner storage layers, enabling lower write current while maintaining thermal stability
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The proposed structure achieves lower Mst with suppressed coercive force (Hc) and improved write error rate (WER) and ballooning, maintaining thermal stability and reducing write current, thus enhancing the performance of magnetoresistance effect elements.
Implementation Method 1
Incorporating an oxide layer adjacent to the storage layer containing a rare earth element and boron (B) improves perpendicular magnetic anisotropy
Implementation Method 2
enhancing wettability and reducing agglomeration
Data Source
AI summary
According to one embodiment, a magnetic memory device includes a stacked structure including a first magnetic layer having a variable magnetization direction, a second magnetic layer having a fixed magnetization direction, a non-magnetic layer provided between the first magnetic layer and the second magnetic layer, and an oxide layer provided adjacent to the first magnetic layer, the first magnetic layer being provided between the non-magnetic layer and the oxide layer, and the oxide layer containing a rare earth element, boron (B), and oxygen (O).